Interpretive Summary: Freezing stress is an important limitation to potato production worldwide. There is a great difference in the natural frost tolerance of various wild potato species, but the physiological factors which promote frost hardiness are poorly understood and have been difficult to investigate. Maintenance of cell membrane integrity seems to be important to frost tolerance, and calcium appears to play an important role in cell membrane integrity. Thus, we sought to investigate the relationship between tissue calcium and frost tolerance. Field application of fertilizer calcium tended to promote additional frost hardiness, particularly in species known to be relatively frost hardy already. It appears that these wild potato species are useful tools with which to characterize the role of calcium in frost tolerance. As we better understand this role of calcium, we will be more able to manipulate it for economic benefits to the cultivated potato crop.

Technical Abstract:
Potato is one of the most important crops worldwide. Frost damage to the foliage is a common problem where potatoes are grown and results in extensive reductions in tuber yield. In contrast to the commercially cultivated potato (S. tuberosum), some wild potato species possess different levels of cold tolerance and/or acclimation capacity. Previous studies suggest Ca2+ as an important factor in the maintenance of membrane integrity and membrane transport functions. The main objective of the present study was to find out if supplemental calcium fertilization could increase the levels of freezing tolerance in different potato species. For this purpose, the freezing tolerance of a broad spectrum of the Solanum taxa was evaluated with and without supplemental calcium fertilization. Most of the species that were grown in the field with extra calcium supplements showed somewhat greater frost resistance, and this effect was usually more evident among the frost hardy species. Future breeding schemes may be able to use this information for selecting frost tolerant clones or clones that would respond positively to calcium fertilization in terms of frost survival.